<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/Users/erlendbasso/.cargo/registry/src/github.com-1ecc6299db9ec823/libm-0.2.6/src/math/log10f.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>log10f.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceSerif4-Regular-1f7d512b176f0f72.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceSerif4-Bold-124a1ca42af929b6.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../../static.files/rustdoc-6827029ac823cab7.css" id="mainThemeStyle"><link rel="stylesheet" id="themeStyle" href="../../../static.files/light-ebce58d0a40c3431.css"><link rel="stylesheet" disabled href="../../../static.files/dark-f23faae4a2daf9a6.css"><link rel="stylesheet" disabled href="../../../static.files/ayu-8af5e100b21cd173.css"><script id="default-settings" ></script><script src="../../../static.files/storage-d43fa987303ecbbb.js"></script><script defer src="../../../static.files/source-script-5cf2e01a42cc9858.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../static.files/main-c55e1eb52e1886b4.js"></script><noscript><link rel="stylesheet" href="../../../static.files/noscript-13285aec31fa243e.css"></noscript><link rel="alternate icon" type="image/png" href="../../../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../libm/index.html"><img class="rust-logo" src="../../../static.files/rust-logo-151179464ae7ed46.svg" alt="logo"></a><form class="search-form"><span></span><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../static.files/wheel-5ec35bf9ca753509.svg"></a></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><a href="#1" id="1">1</a>
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</pre><pre class="rust"><code><span class="comment">/* origin: FreeBSD /usr/src/lib/msun/src/e_log10f.c */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* See comments in log10.c.
*/
</span><span class="kw">use </span>core::f32;
<span class="kw">const </span>IVLN10HI: f32 = <span class="number">4.3432617188e-01</span>; <span class="comment">/* 0x3ede6000 */
</span><span class="kw">const </span>IVLN10LO: f32 = -<span class="number">3.1689971365e-05</span>; <span class="comment">/* 0xb804ead9 */
</span><span class="kw">const </span>LOG10_2HI: f32 = <span class="number">3.0102920532e-01</span>; <span class="comment">/* 0x3e9a2080 */
</span><span class="kw">const </span>LOG10_2LO: f32 = <span class="number">7.9034151668e-07</span>; <span class="comment">/* 0x355427db */
/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
</span><span class="kw">const </span>LG1: f32 = <span class="number">0.66666662693</span>; <span class="comment">/* 0xaaaaaa.0p-24 */
</span><span class="kw">const </span>LG2: f32 = <span class="number">0.40000972152</span>; <span class="comment">/* 0xccce13.0p-25 */
</span><span class="kw">const </span>LG3: f32 = <span class="number">0.28498786688</span>; <span class="comment">/* 0x91e9ee.0p-25 */
</span><span class="kw">const </span>LG4: f32 = <span class="number">0.24279078841</span>; <span class="comment">/* 0xf89e26.0p-26 */
</span><span class="attr">#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
</span><span class="kw">pub fn </span>log10f(<span class="kw-2">mut </span>x: f32) -> f32 {
<span class="kw">let </span>x1p25f = f32::from_bits(<span class="number">0x4c000000</span>); <span class="comment">// 0x1p25f === 2 ^ 25
</span><span class="kw">let </span><span class="kw-2">mut </span>ui: u32 = x.to_bits();
<span class="kw">let </span>hfsq: f32;
<span class="kw">let </span>f: f32;
<span class="kw">let </span>s: f32;
<span class="kw">let </span>z: f32;
<span class="kw">let </span>r: f32;
<span class="kw">let </span>w: f32;
<span class="kw">let </span>t1: f32;
<span class="kw">let </span>t2: f32;
<span class="kw">let </span>dk: f32;
<span class="kw">let </span><span class="kw-2">mut </span>hi: f32;
<span class="kw">let </span>lo: f32;
<span class="kw">let </span><span class="kw-2">mut </span>ix: u32;
<span class="kw">let </span><span class="kw-2">mut </span>k: i32;
ix = ui;
k = <span class="number">0</span>;
<span class="kw">if </span>ix < <span class="number">0x00800000 </span>|| (ix >> <span class="number">31</span>) > <span class="number">0 </span>{
<span class="comment">/* x < 2**-126 */
</span><span class="kw">if </span>ix << <span class="number">1 </span>== <span class="number">0 </span>{
<span class="kw">return </span>-<span class="number">1. </span>/ (x * x); <span class="comment">/* log(+-0)=-inf */
</span>}
<span class="kw">if </span>(ix >> <span class="number">31</span>) > <span class="number">0 </span>{
<span class="kw">return </span>(x - x) / <span class="number">0.0</span>; <span class="comment">/* log(-#) = NaN */
</span>}
<span class="comment">/* subnormal number, scale up x */
</span>k -= <span class="number">25</span>;
x <span class="kw-2">*</span>= x1p25f;
ui = x.to_bits();
ix = ui;
} <span class="kw">else if </span>ix >= <span class="number">0x7f800000 </span>{
<span class="kw">return </span>x;
} <span class="kw">else if </span>ix == <span class="number">0x3f800000 </span>{
<span class="kw">return </span><span class="number">0.</span>;
}
<span class="comment">/* reduce x into [sqrt(2)/2, sqrt(2)] */
</span>ix += <span class="number">0x3f800000 </span>- <span class="number">0x3f3504f3</span>;
k += (ix >> <span class="number">23</span>) <span class="kw">as </span>i32 - <span class="number">0x7f</span>;
ix = (ix & <span class="number">0x007fffff</span>) + <span class="number">0x3f3504f3</span>;
ui = ix;
x = f32::from_bits(ui);
f = x - <span class="number">1.0</span>;
s = f / (<span class="number">2.0 </span>+ f);
z = s * s;
w = z * z;
t1 = w * (LG2 + w * LG4);
t2 = z * (LG1 + w * LG3);
r = t2 + t1;
hfsq = <span class="number">0.5 </span>* f * f;
hi = f - hfsq;
ui = hi.to_bits();
ui &= <span class="number">0xfffff000</span>;
hi = f32::from_bits(ui);
lo = f - hi - hfsq + s * (hfsq + r);
dk = k <span class="kw">as </span>f32;
dk * LOG10_2LO + (lo + hi) * IVLN10LO + lo * IVLN10HI + hi * IVLN10HI + dk * LOG10_2HI
}
</code></pre></div>
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